*M Series is recommended for reliable ignition, durability and anti-carbon buildup under high load.

The Iridium alloy is used because of its durability and reliability. On an average plug, a narrow core typically shortens life span of plug but with the intense durability of iridium there is no sacrifice in any longevity. With a high melting point of 2454 degrees C, opposed to the 1769 degrees C of white gold, the electrode can tolerate the high levels of compression and minor knocking without any deterioration. A nickel coating on the housing also prevents the spark plug from premature deterioration. The Iridium plugs are available for multiple applications and offered in “colder” heat ranges of 7 and up and specifically for rotary, heat ranges of 9 and up are offered.